How to Plant Onions at Home: Basic Growing Guide

If you’re planning on adding onions to your vegetable garden, that’s a good idea. Many beginner gardeners find them easy to grow.

Onions take 90 to 100 days to reach maturity when planted from seeds.

In most climates, the best time to plant them is in early spring to mid-spring. For those living in warmer climates, autumn is a good time to plant.

Below is a basic guide on how to grow onions at home:

How to Grow Onions From Seed

Start the seeds indoors in a container with rich compost or potting soil. However, it’s best to start them 8 to 10 weeks before you plan to transplant them outdoors into the garden.

Soak the seeds first before planting for better germination. Also, follow the packaging details, as instructions may vary by climate and onion variety.

Keep the soil moist and place the container in a warm area until the seeds sprout. Once they sprout, place the container in a cool area where it gets ample light.

Transplant the seedlings when they are mature enough.

Planting Onion Sets

Onion sets are miniature bulbs that, once put into the soil, will develop into full-size bulbs after 3 to 4 months.

These are a bit more robust and grow much faster than seeds. Plant approximately 4 inches apart in rows 12 to 18 inches apart.

Also, do not bury them more than an inch deep into the soil. For best results, soak the sets in compost tea for 15 minutes before planting.

Additionally, when picking up bulbs at a nursery, you should check that they are dry (typically bought in mesh bags) and firm.

Spacing 

Spacing will be dependent on whether you are planting your onions from seedlings or sets.

When planting the seedlings, space them about 6 inches apart when transplanting. Closer spacing will produce smaller bulbs. The rows should also be about 12 inches apart.

When doing sets, plant them about 2 to 3 inches apart. Also, add straw mulch between sets and in between the rows. Allow for 12 to 15 inches of spacing between rows.

How Deep to Plant?

Sink seeds a quarter inch deep into the soil. If planting from sets, place them approximately one inch down into the soil where they can take root.

Remember, the type of onion will also determine how deep you’ll put it in the ground. It is crucial to know your climate and onion variety to fully understand their growing needs.

Watering 

For onion plants to produce high yields, they need adequate water. Therefore, provide about an inch of water per week.

Also, it is best to utilize mulch around the plants, as it will help keep the soil moist and weed-free.

Fertilizer Requirements

To flourish, onions require rich, fertile soil that is well-drained.

They also require an adequate amount of nitrogen for proper growth and development [1]. Therefore, apply a nitrogen-based fertilizer three weeks before planting and then again three weeks after.

Phosphorus and potassium are nutrients they’ll also need, especially in the early stages. Additionally, spread some compost among the plants and rake it into the soil.

Growing From Scraps

It is also possible to grow onions from scraps. In fact, onion is one of the easiest vegetables to grow from scraps [2].

• Cut off the root end and use toothpicks or other materials that can hold the scrap in place over a cup or bowl.
• Next, fill the dish, jar, or container with water and suspend just the root end in the water.
• Soon you’ll start to see tiny sprouts coming out of the top and root-like tentacles from the bottom.
• Afterward, place the sprouted scrap in the ground or a pot, covering it until just the sprouts are above the soil line.
• Finally, water, fertilize, and cultivate as you would with an onion that is grown from seed or set.
  

Another source says to regrow onions from scrap, just cut off the root end and plant it directly in moist soil in a sunny location.

Growing in Containers

You can grow onions in shallow containers that are at least eight inches deep, either from sets or seeds.

• Fill the container about halfway with soil, and keep it watered but well-drained once planted.
• Add rich compost until the bulbs appear.
• The bulb should remain at least an inch under the soil, and if exposed, cover it up.
• Additionally, cut back the leaves to help the plant focus more fully on the development of the bulbs.
  

Onion Companion Plants

Anything in the cabbage family makes a great companion plant for onions.

Onions also help to deter aphids, Japanese beetles, carrot flies, and rabbits, so any crop that these pests enjoy can be planted together with onions.

Lettuce and carrots are also good options. They have very different root systems that won’t compete for the same soil resources as onions. Tomatoes, lettuce, and strawberries are other great companions for onions.

Strawberries are also good companions. However, avoid all varieties of peas and beans, as they do not grow well near onions.

Harvesting

How do you know when onions are ready? Firstly, the top green leaves that start to wilt are an indication that they are near harvesting. The bulbs will continue into maturity as the leaves start to lose their color.

However, if any of the plants have flowers on the stalks, they should be harvested immediately.

When harvesting, pull on the tops to safely remove the whole plant from the soil. Next, shake the dirt off around the bulbs.

Finally, let the bulbs sit in the garden for 1 to 2 days to allow natural drying.

Pests and Diseases

• The onion fly is one of the most prolific pests that affect the allium family. They lay eggs and hatch maggots that feed on the seedlings. This fly resembles the house fly.
• The lesser bulb fly looks similar but is smaller. Once infected by them, the plants must be dug up and destroyed.
• Thrips are another insect that lays eggs on the leaves and then suckers up the plant sap.

There may also be many diseases due to uncontrolled watering, resulting in lesions and a rot. Onion plant diseases include soft rot, purple blotch, damping off, downy mildew, and onion smut.

Storing 

Store onions in dry and cool locations. If it is too moist or warm, resprouting can occur.

Mesh bags, bushel baskets, or cardboard boxes with holes provide the best storage to keep them dry and cool for the short term.

However, keep in mind that onions will only last about seven to ten days before thoroughly drying out or resprouting, even in the best conditions.

See also: How to Plant Garlic: A Basic Growing Guide.

Takeaway

Planting onions in your garden can be a rewarding venture. Whether you start with seeds or sets, various factors will determine how well your harvest turns out.